/*
 * Copyright 2002-2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.core;

import org.springframework.lang.Nullable;

/**
 * Interface defining a generic contract for attaching and accessing metadata
 * to/from arbitrary objects.
 *
 * @author Rob Harrop
 * @since 2.0
 */
public interface AttributeAccessor
{

    /**
     * Set the attribute defined by {@code name} to the supplied {@code value}.
     * If {@code value} is {@code null}, the attribute is {@link #removeAttribute removed}.
     * <p>In general, users should take care to prevent overlaps with other
     * metadata attributes by using fully-qualified names, perhaps using
     * class or package names as prefix.
     *
     * @param name  the unique attribute key
     * @param value the attribute value to be attached
     */
    void setAttribute(String name, @Nullable Object value);

    /**
     * Get the value of the attribute identified by {@code name}.
     * Return {@code null} if the attribute doesn't exist.
     *
     * @param name the unique attribute key
     * @return the current value of the attribute, if any
     */
    @Nullable
    Object getAttribute(String name);

    /**
     * Remove the attribute identified by {@code name} and return its value.
     * Return {@code null} if no attribute under {@code name} is found.
     *
     * @param name the unique attribute key
     * @return the last value of the attribute, if any
     */
    @Nullable
    Object removeAttribute(String name);

    /**
     * Return {@code true} if the attribute identified by {@code name} exists.
     * Otherwise return {@code false}.
     *
     * @param name the unique attribute key
     */
    boolean hasAttribute(String name);

    /**
     * Return the names of all attributes.
     */
    String[] attributeNames();

}
